What is MU-MIMO? Explained!

MU-MIMO stands for multi-user, multiple-input, multiple outputs. Now MU-MIMO was introduced with the wave 2 version of the 802.11ac wireless standard and this is a feature that’s used in modern wi-fi routers. And what this does is that it allows multiple wireless devices to communicate with a wi-fi router at the same time.

Now previously routers communicated with devices using SU-MIMO which stands for single-user, multiple input, multiple outputs. Now, this was used with the previous wireless technology which was 802.11n. Now, this also allowed wi-fi routers to communicate with multiple devices but only with one device at a time. So, each device would have to wait its turn to communicate with the router. So as more devices connected to the wi-fi router, congestion happens.  

Now this is not really a big deal if these devices were just using low data applications such as browsing the internet. However, if they were using high data applications, such as streaming videos, then the result would be a slowdown in the internet speed which would cause lag and buffering.

So basically SU-MIMO works on a first come first serve basis.  However, a router that’s using MU-MIMO all the devices that are connected to it won’t have to wait their turn because it allows communication to multiple devices all at the same time. It breaks up the internet bandwidth and pushes it to the connected devices. So, with this technology, you will see a significant improvement in the speed of your internet especially if you’re doing things that require a lot of bandwidth, such as streaming videos or downloading. It reduces lag to the connected devices because the connection is never interrupted, which increases performance. So, it’s almost as if each device had its own separate wi-fi router. So, if you have a lot of wireless devices that demand a lot of bandwidth in your home and you’re experiencing slow internet performance or choppy video, you should be using a router with MU-MIMO technology.

Now MU-MIMO also takes advantage of beamforming. Now beamforming is a technique that sends transmissions in a specific direction which strengthens a signal.  But without beamforming, the transmission is sent in every direction which can weaken the signal and this is what happens in older routers.

MU-MIMO,What is mu-mimo, What is MU-MIMO? Explained!, TechRX

But with newer routers, the signal is directed to the devices that are connected to it. So basically, you can compare this technique to a flashlight versus a lantern. A lantern works without beamforming, where light is spread out in every direction and not towards a specific device. But a flashlight works similar to beamforming. where the light is specifically aimed at a certain direction and targets specific devices.  Now MU-MIMO routers come in different variations. So, for example, they may come in 2×2, 3×3, or 4×4 versions. And these variations refer to the number of streams that are created. So, a 2×2 device means that it has 2 antennas that are used for 2 simultaneous streams. A 3×3 device means it has 3 antennas for 3 streams. And a 4×4 device will have 4 streams. Now, this doesn’t mean that you can’t add more devices. So, for example, on a 4×4 router if you add a fifth device, then that just means that a stream will have to be divided and shared with another device. But with the new wi-fi 6, it will have even more dedicated streams for your devices.

MU-MIMO,What is mu-mimo, What is MU-MIMO? Explained!, TechRX

So, the more devices you add, the more streams won’t have to be shared as much. In fact, some newer wi-fi 6 routers can support 12 simultaneous streams, with 4 streams on a 2.4 GHz band and 8 streams on the 5 GHz band. Now not all wi-fi routers will support MU-MIMO. Because in order to have this technology, the router must support at least the 802.11ac wave 2 standard which is known as wi-fi 5. Because the previous versions, such as the 802.11a, b, g, and n, do not support it. And the router must specifically state that it supports MU-MIMO. And also, the devices that connect to this technology must also support it, which most modern devices today already do. And in addition, they also need to be able to connect to the 5 GHz band because MU-MIMO only works in 5 GHz in wi-fi 5.  So older devices that can only connect to the 2.4 GHz band will not be able to take advantage of MU-MIMO.  And another thing to remember is that MU-MIMO only affects the download link and not upload and it only supports a limit of 4 simultaneous streams.  

However, with the new 802.11ax standard, which is known as wi-fi 6, works both in 2.4 GHz and 5 GHz and it can support 8 or more simultaneous streams and as I said before, some of these newer routers can support 12 simultaneous streams.  


  • MU-MIMO,What is mu-mimo, What is MU-MIMO? Explained!, TechRX

    My name is Biplab Das. I’m the leader of TechRX and Founder of and Professionally I'm a full-time IT support engineer whose childhood obsession with science fiction never quite faded. A quarter-century later, the technology that I coveted as a kid is woven into the fabric of everyday life. People say smartphones are boring these days, but I think everyone is beginning to take this wonderful technology marvel for granted.

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